1. Field of the Invention
The present invention relates to a compressor which, for example, can be utilized in an air conditioning system for a vehicle.
2. Description of Related Art
In a known compressor, which can be utilized in an air conditioning system for a vehicle having a housing, a crank chamber is formed for storing therein a driving mechanism for operating a piston stored in a cylinder bore. Namely, under the action of the driving mechanism, an axial reciprocating movement is imparted to the piston, thereby executing a compression cycle, which consists of a series of operating periods, which includes a sucking of a refrigerant gas as a fluid to be subjected to a compression, a compression of the sucked gas and a discharge of the compressed refrigerant gas to an outside refrigerant system.
In the above mentioned compressor, lubrication of parts subjected to sliding movements relies on a flow of lubricant into the compressor together with the flow of the refrigerant gas. In other words, the lubricant is mixed with the refrigerant gas to be compressed. As a result, the discharge of the compressed gas to the outside refrigerant system causes the lubricant mixed therewith to be discharged, which causes the amount of the lubricant to be reduced, thereby causing the lubrication to be insufficient.
Furthermore, a change in the capacity in the above mentioned type of the compressor is, for example, done by adjusting the pressure at the crank chamber. Namely, a change of the pressure at the crank chamber causes a pressure difference to vary between the crank chamber and the cylinder bore. On the other hand, a shortage of the lubricant in the compressor causes an excessive heat to be generated at the sliding parts in the compressor, which causes the pressure to be increased at the crank chamber. Such an increase in the pressure at the crank chamber causes the capacity to be reduced. In short, a stable control of the capacity cannot be done.